Means for unblocking lenses



' Oct. 7,1947. I D. DODKIN I 2,428,412 MEANS FOR UNBLQCKING LENSES Filed Feb. 15, 1942v TO REFRIGER TO REFRIGE'R ANT X TO REFRIGE'RANT oozv/ua. book/N INVENTOR TTORNEY Patented Oct. 7, 1947 UNITED PAT-EN T ()2FlUC li'.

to American Optical. Company,

' Southbridge,

Mass, a'voluntary association .ofTMassachusetts Application-February 13, I942, s-eriarno. 43037 30 2 Claims.

1 This invention pertains to improved means for unblocking'lenses or materials having the characterof lenses. In the optical industry,'lenses that -req'uire an optical surface are 'of necessity ground and polished. ing operation necessitates some means for holding the-lens on --a given axis :so that 'the'true optical surface will result.

The'metho'd of securing the lemon *a given axis is-ordinarily obtained by securing the lens blankto-a'lens block, "which lens blank is secured to saidblock by a bonding material. 'One of the convention-al bonding materials now in wide use is pitch. After onesurface of the lens'blank isadequately treatedyit is necessary to remove i the lens or the lens "blank from the lens block. Heretofore, the-lens or lens'blank was removed fromthe lens block by. placing the lens 'and'lens block under astreamof watenor bysubjectin'g it to some cooling medium-such as by placing'it in an ice box. While various methods for .unblocking the lens or lens blank from the lens block areused, they all require the amount of time that ordinarily involves minutes.

'The'present'invention' contemplates the useof 1 a'refrigerant tocool a fluid bath so that the'lens bloc-k maybe suitably immersed in the fluid bath to provide'the necessary cooling ofthepitch'between the lens'orlens blank and the lens block. The ordinary pitch-now in useforthe purpose of blocking lenses has a coeflicient of expansion about ten timesas great as'that-ofthe average lens. It can be reasonably said that the coeflicient of expansion ratio between'pitch'and'glass is -.about'ten to one. It will therefore be seen that by cooling thelens block, the pitch and lens medium will both be cooled, butbecauseof the ten to --one ratio, the 'pitch Will "contract =much more rapidly than the lens so that the lens will be freed from thepitch.

:Employing the present method, a fiuid bath 4 is used in which the lens blocks are substantially immersed. Because of-the mobility of-thefluid, which is cooled by a refrigerant, there results an intimate contact-between the cooled fluid andthe lens block. "Since the fluid will have an "equal distribution about the lens a block, -a substantially uniform cooling of the lens block will produce substantially uniform cooling ofthe'pitch andthe lens sothatthe contraction of thepitch, which is-more rapid than the glass, will cause "a clean severancebetween-the glass and the pitch.

It is therefore an object of the invention to provide an improved #means 'of unblockin'g a lens or lens blank by subjecting the lens block tothe The grinding "and polish- 2 acti'onof a cooling medium, "which-medium is cooled by ag'aseous or quasi-gaseousrefrigerant.

It is'a further object of the invention "to-provide ameans'- of unblocking *lensesby cooling the lensbl'ocks in a bath of fluid having a very low freezingp'oint, said bath being cooled by a gaseo'us or quasi-gaseous refrigerant.

A further object of the invention is'to provide a refrigerating tank'suppliedwith a coolingagent which lowersthe temperature of a fluid-bath in intimate contact with the lens block.

A further object of the invention is to.provide novel means of unblockinglenses or the like-by subjecting lens blocks to a fluidmedium, "which fluid me diumiis directly cooledby a Stream of refrigerant. V

A further object is to provide alen-s unblocking apparatus'having means for suspending the lens blocks in'a liquid bath which is 'cooled'by a refrigerant.

'In 'the clraWiIigs:

"Fig/1 is a se'ctionalviewof ata'nk somewhat like the tank shown in Fig.-'3 except that a refrigeran't chamber therein is separated from"the' compartment carrying the fluid cooling medium. I Fig.2"is' a sectionalvie'w taken along lines 22 of Fig.3 showing a m'ulti-orificed nozzle immersed tame cooling fluidbelow thelens blocks.

3-is a top view of Fig. 2 showing ther'elative position'ofthe orificed'noz'zle inrelatio'n to *the lens blocks within the cooling tank.

Referring tothe drawings and more particularly to' Fig. 1,'a cooling tank-dhas an outer'insulating layer onthe si'des and the bottom. The tank has a lower chamber 6 with a plurality of spaced baiiies securedto the bottom of the tank.

- A-spaeingm'emberfS separates the lower chamber fi' from the upper chamber 9. The spacing memberissupported by ribs Ii onthe-underneathside thereof, w'ith the spacing member preferably being made oftthin metal and ha'ving a water tight connection with the side walls of "the -metallic liner l l of the tank 4.

Amok "I 2 is fonned'o'f longitudinally disposed wires it which are U shaped so that 'their'e ends thereof rest 'onthe topside 'of the spacing member 8. Cross-wires mar-e 'sha'ped'substantially'the same as the-longitudinal wires 3 and disposed la'terally thereof and are sufficiently close together so that a series of square-shaped supports are provided by the longitudinal and cross -wires to permit the shank 15' of the lens block's 1 5 to be insertedth'erein so that the lens blocks are supported with thelenses T6 above the fluid l1.

is on one end of the pipe coupling is disposed internally of the chamber 6. A lock nut 2% on the pipe connection 22 holds the jet 23 in place withw in the lower chamber 6. An opening 25 is pro-f vided in the lower chamber 6 through the metallic liner H and the insulation 5 so that an escapeis provided for the chamber 6 to eliminate any I substantial back pressure when the refrigerant is supplied in the lower chamber.

Fig. 2 shows a tank 26 having an inner liner 2'1 and an insulating portion 28 on the sides and botshown by the arrows through the lower chamber 1 6 so that the liquid medium I! may reach a sufficiently low temperature to properly cool said liquid N. I

In Fig. 2, the liquid refrigerant coming from the jets 34 and the nozzle3l is preferably carbon dioxide, which is utilized as a refrigerant as set [forth in reference to Fig. 1, except thatin Fig. 2

the'refrigerant emerges through the jets 34 directly into intimate contact with the cooling fluid 3S'so that the cooling fluid acts as a medium to chill the lens blocks 38.

While carbon dioxide has been set forth as a preferred refrigerant, other refrigerants may be used such as ethane C206, propylene CsI-Is, and

propane CzHc. The cooling fluid Her 36 may be ethyl-alcohol which has a freezing point of ap-.

proximately 1li C. or methyl alcohol which tom of the tank 25. Apipe connection 29 is con 7 nected to the fluid chamber 33 and has a nozzle 3i connected on one end thereof, which nozzle and pipe connection are secured to the metallic liner 21 by means of nuts 32 and 33. The nozzle 3! has a plurality of jets 3.6 on the underneath side thereof, and a cap 35 on the end of the nozzle 3i so that the refrigerant entering the tank 26 through the pipe connection 29 will be urged through the jets 3d and into the fluid 36 in the tank 25.

A rack 31' is formed in much the same manner:

as the rack l2 in'Fig. l. The rack 31, shown in Fig. 2, is used to support the lens blocks 38 thereon so that the lenses 39 ma be close to the surface of the cooling fluid 36. v

Fig. 3 is a top View of the section shown in. Fig.

' 2 and shows the tank 26 having the inner liner 2'! with the insulation 28'on the outside thereof.

7 In Fig. 3 the rack 37 is shown having the squares therein which provide the support for carrying the lens blocks 38 and the lenses 39, with said lenses 39 being supported above the surface of the cooling fluid .36.. V V

Fig. 3 shows three nozzles 36 which are connected to the pipe couplings 29 with the caps 35 connected on the free ends of the various nozzles.

The number of nozzles, the number of jets in the nozzles, the location of the jets in relation to the lens blocks, and the distance of the lens blocks above the jets, are simply illustrative and any arrangement or dimension of parts maybe employed depending upon the desired results. 7 V l g The refrigerant which enters the jet in Fig. 11 will pass over thetops of thebaflies 1 and underother suitable refrigerant.

has a freezing point of approximately j97 C.

Ethylene glycol may be mixed with water so that approximately 52.5% of the mixture is ethylene glycol, which will result in a cooling fluid having a fr ezing point of about l0 Ce 'Kerose'ne having a freezing point of about 56 0., and acetone having a freezingpoint of'about 95C. may

also be used as a cooling fluid. '5 From the foregoing, it will be seen that where the liquid refrigerant is used, the liquid changes to a gas to absorb the latent heat of'vaporization. Under any condition, whether a liquid or gas is used, it'will still be expanding when in operation so that an adequate cooling is obtained. The refrigerants utilized. may be compressed into a tank and when the critical pressure is obtained within the tank, or compression chamber, the

gasbecomes a liquid. I

The cooling fluid used, under any condition would ordinarily be such that it would not freeze when used in an unblocking system as set forth herein'in conjunction with any of the refriger ants set forth in the application or with any While the present disclosure shows that the lens blocks only, are immersed in the cooling" fluid, under certain conditions the entir'e lens block and its lens may be immersed in the liquid bath. However, the present disclosure is suflicient to show that the mobility of the cooling liquid will cause intimate engagement with a.

neath the bottom of the baflies l9 so that there is a" definite path for. the refrigerantgThe fluid ll; in Fig. l, touches one-wall of the chamber 6 so that the fluid I? may be sufficiently cooled so that when the lens blocks are disposedin the fluid, there will be'a substantially uniform cooling of the lens blocks. I

In Figs. 2 and 3, the refrigerant has a. pressure exerted in the direction shown by. the arrows a: sothat the refrigerant is ejected from thejets 34 into the fluid cooling medium 35. 7

The preferred refrigerant for use in conjunction with the present 'inventionis set forth as I being carbon dioxide v(CO2) ,since carbon dioxide is ordinarily readily available, and is easy to handle; The carbondioxide is crdinarily stored' in a compression tank and may be in a liquid or; a gaseousform. When the control valve 2i, is opened (Fig. l) the CO2 flows in the direction major portion of the lens blockso that adequate cooling being throughout the lens block will'cause a rapid severanceof the lens from the pitch due to the difference in the coeflicient of. expansion between thepitch and the lens.

. In utilizing the present disclosu re, the lenses." are unblocked rapidly and the'sides of the lenses 7 or lenses'blanks thatengaged the pitch will'be substantially, if not entirely, free from any pitch 7 particles;

Th present invention is more rapidand more.

efficient than any commercial method heretofore known and reduces the time for unblockinga single lens from thatbf minutes to thatof seconds. V r Having described my invention, I;claimi 1. In a device of the character described for unblocking lenses, the' combination of a 'recepf tacle adapted to contain a' fluid,"a rack in there ceptacle 'forsupporting at least one lens block havin a lens adhesively secured thereto, said rack being spaced from the bottom of the receptacle, a cooling fluid in f the receptacle to a 1 level sufficient to ,}cover the rack and immerse substantially the whole of the lens'blocl; without 7. contacting theuens adhesively'secured; thereto, 7

nozzle means extending within the receptacle and disposed below the rack, said nozzle means having a plurality of jets therein, and a source of refrigerant connected with the nozzle means, the refrigerant being held under compression at the source and adapted upon ejection from the jets of the nozzle to expand and chill the cooling fluid.

2. In a devic of the character described for unblocking lenses, the combination of a, receptacle adapted to contain a fluid, a rack in the receptacle for supporting at least one lens block having a lens adhesively secured thereto, said rack being spaced from the bottom of the receptacle, a cooling fluid in the receptacle to a level sufficient to cover the rack and immerse substantially the Whole of the lens block without contacting the lens adhesively secured thereto, said fluid having a freezing point lying between -40 C. and 114 C., nozzle means extending within the receptacle and disposed below the rack, said nozzle means having a plurality of jets therein, and a source of refrigerant connected with the nozzle means, the refrigerant comprising CO2 held under compression at the source and, adapted upon ejection from the jets of the nozzle to expand and chill the cooling fluid.

DONALD DODKIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

